The present invention relates to a seat belt retracting device to be mounted on a vehicle, such as a passenger vehicle and, more specifically, to a seat belt retracting device comprising a motor for retracting, or retracting and unwinding of the seat belt.
The seat belt retracting device to be mounted on the automotive vehicle or the like has a function to wind up the excessive portion of the unwound seat belt after the passenger seated on the seat pulls the seat belt out and attaches the tongue to the buckle unit. In order to realize this function, a single return spring is generally used in the conventional seat belt retracting device. When fastening the seat belt, a passenger pulls out the seat belt against the energy of the return spring, and when he or she engages the tongue with the buckle and moves the hands off, the excess portion of the belt that has been pulled out is retracted by a force of the return spring back into the seat belt retracting device until the seat belt fits to the human body.
The seat belt retracting device necessarily satisfies the following objects simultaneously: (1) to reliably retract the excessively pulled out seat belt until it fits to the human body, and when it is not worn by a passenger, to retract the seat belt that is pulled out into the receiving portion completely; and (2) to not give the passenger a feeling of being excessively pressed on his or her breast or the like when the belt is normally fastened.
However, when a spring is used that has less energy to reduce the passenger""s feeling of being excessively pressed on his or her torso, the retracting force to retract (store) the belt is lowered, thereby lowering the operability and storability. In contrast, when a spring having a stronger energy is used, the retractor exhibits a sufficient retracting force when retracting the seat belt, and the passenger""s feeling of being excessively pressed on his or her torso when the seat belt is normally fastened increases.
One suggested way to solve this tension problem is a method of using a motor in conjunction with a return spring for retracting the seat belt, as disclosed for example in Japanese Patent Publication Application No. 9-132113.
When retracting, or retracting and unwinding the seat belt with a motor alone, detectors such as a buckle switch or a limit switch for detecting manual unwinding of the seat belt are provided and the output thereof is fed to the microcomputer-based electrical circuit to drive the motor by the output from the electrical circuit.
The electrical circuit is formed by mounting circuit elements on the printed board having a printed wiring thereon and treated as a separate unit from the body of the seat belt retractor (in this specification, a unit of mechanical parts having a function to transmit a force of the return spring or the motor to the retracting spool which retracts the seat belt is referred to as the body of the seat belt retractor).
FIG. 5 shows a structure of the conventional seat belt retracting device and an example of connection therein. The body of the seat belt retractor comprises a limit switch for detecting unwinding of the seat belt and a motor installed therein. The electrical circuit being a separate unit comprises an external input circuit, a logic power supply unit, a CPU, a sensor input circuit, a noise filter, and a motor drive circuit and so on, which are, as shown in the figure, composed of a plurality of parts such as a general purpose IC, a condenser, and a resistance all mounted on the printed board. The wiring between the buckle switch, battery, and the seat belt retractor body are made by a wire harness, and connected to the printed board.
FIG. 6 shows an advanced example of such a device. In FIG. 6, the electric circuit comprises a communication unit in addition to the circuits shown in FIG. 5, and information is sent to and received from the collision prediction sensor circuit via an electronic communication. The external input circuit can be connected with a child seat switch for detecting whether or not a child seat is mounted, and a service board to be used by the vehicle manufacture for adjustment. There is also provided a control output circuit, so that the solenoid in the body of the seat belt retracting device can be controlled.
In the construction shown in FIG. 5 and FIG. 6, since the electric circuit is composed of a plurality of components, there is a problem in that the number of the components increases and thus the manufacturing cost increases. There is another problem in that a number of processes are required when assembling since the connection between each unit is made by a wire harness. There is still another problem in that the possibility of malfunction caused by imperfect connection may be increased.
With these circumstances, it is an object of the present invention to provide an electric circuit in which the number of components that constitute the electric circuit is decreased, and the cost for wiring can be reduced.
The first embodiment for solving the problems described above is a seat belt retracting device having a motor for retracting, or retracting and unwinding the seat belt, wherein the electric circuit for controlling operation of the motor comprises a one-chip integrated circuit (xe2x80x9cICxe2x80x9d).
In this embodiment, since the electric circuit for controlling operation of the motor (the portion shown as an electric circuit in FIG. 5 and FIG. 6 for controlling the sensor, solenoid, and the motor) comprises a one-chip IC, the number of the components can be significantly reduced in comparison with the conventional electric circuit, and the circuit may be miniaturized as a whole.
The second embodiment for addressing the problems described above is the first embodiment, but with the one-chip IC mounted on the body of the seat belt driving unit.
Since the circuit can be miniaturized as a whole by constituting the electric circuit by a one-chip IC, the IC can be mounted on the body of the seat belt driving unit. Accordingly, the wiring to the motor, or the wiring to the limit switch for detecting the seat belt retraction can be made within the body of the seat belt driving unit without a wire harness or a connector, thereby facilitating assembly of the seat belt driving unit to the vehicle, and the problem of imperfect connection is reduced because the number of connectors is reduced. Efficiency in terms of the space is improved by utilizing the case portion of the body of the seat belt driving unit for mounting the one-chip IC.
The third embodiment for solving the problems described above is the second embodiment, with at least a part of the wiring within the body of the seat belt driving unit out of the wirings connected to the one-chip IC, the motor, and the detector for controlling the motor is formed integrally with the case or the plate within the body of the seat belt retracting device. At least a part of the wiring within the body of the seat belt driving unit is integrally formed with the case or the plate within the body of the seat belt retracting device by insert molding or printed wiring. Accordingly, it is not necessary to perform such wiring within the body of the seat belt retracting device, thereby facilitating the assembling process of the body of the seat belt driving unit.
The fourth embodiment for solving the problems described above is the third embodiment, with the connector for connecting the case or the plate and the wiring from the detector being integrally formed with the case or the plate. Since the connector for connecting the case and the wiring from the detector is integrally formed with the case or the plate, additional connector is not required. Therefore, the wiring to the connector is not necessary, thereby facilitating the assembling process.
The fifth embodiment for solving the problems described above is any one of the first embodiment to the fourth embodiment, with at least one of the control output power circuit, the motor control power circuit, and the communication control power circuit out of the electric circuits comprising a one-chip IC that is not supplied with power in normal condition, but supplied only during the period from the moment at which the unwinding of the belt is detected until the retracting operation of the motor is complete, and during the period that the engagement between the buckle and the tongue is being detected.
At least one of the control output power circuit, the motor control power circuit, and the communication control power circuit needs not to be supplied with power all the time, and thus it may be constructed in such a manner that power is supplied only when the passenger is present and operating the seat belt, and when the passenger is wearing the seat belt. In this embodiment, since these circuits are not supplied with power in normal condition, but supplied with power only during the period from the moment at which the unwinding of the belt is detected until the retracting operation of the motor is complete and during the period that the engagement between the buckle and tongue is being detected, battery power consumed in these circuits may be reduced.
The sixth embodiment for solving the problems described above is any one of the first embodiment to the fifth embodiment, wherein retraction of the belt by the motor is carried out for a first prescribed period of time from the moment at which the disengagement between the buckle and the tongue is detected. The retraction of the belt by the motor is also carried out for the first prescribed period of time after a second prescribed period of time has elapsed from the moment at which the unwinding of the seat belt is detected while the engagement between the buckle and the tongue is not being detected. If the re-unwinding of the seat belt is detected during retraction of the belt by the motor then retraction of the belt by the motor is stopped. Retraction of the belt by the motor is carried out again for the first prescribed period of time after the second prescribed period of time has elapsed without engagement between the buckle and tongue being detected. In this embodiment, retraction by the motor is not carried out while the engagement between the buckle and the tongue is being detected.
In this embodiment, when the disengagement between the buckle and the tongue is detected, retraction by the motor is carried out only for the first prescribed period of time. The first prescribed period of time is normally set in advance to the length during which the seat belt can be retracted completely from the state of being engaged with the buckle. When the fact that the seat belt is pulled out by a passenger is detected, the motor starts retraction of the seat belt after the second prescribed period of time has elapsed. The second prescribed period of time is set in advance to the length of time during which the seat belt can be pulled completely to the state of being engaged with the buckle. In the case where the engagement is not made during this second period of time, it is considered that the passenger has made the pulling action to allow the seat belt to be retracted, and the motor is operated for the first prescribed period of time to retract the seat belt.
When the fact that the seat belt is pulled out by a passenger is detected while the seat belt is being retracted, retraction by the motor is stopped once, and started again after the second period of time has elapsed from that moment. It is because the passenger may want to pull the seat belt again to engage the tongue with the buckle, and in such a case, the action of the passenger should not be hindered.
With this sequence, the seat belt can be more smoothly retracted.